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YOU CAN 3D PRINT A PLATE THAT MAKES A BALL DANCE BY ITSELF

A camera watches a ball on a tilting plate and never lets it fall off, even when you push it.

by aaedmusa

FULL CAD BOM FIRMWARE DOCS

RoboticsDisplays

difficulty
●●●●○
time
a weekend-plus
license
MIT
repo
repo ACTIVE64 stars

WHAT YOU’LL NEED

  • 3D printer + filament — printable parts — files are in the repo
  • Electronic parts — full list with part numbers in the repo BOM
  • Dev board / microcontroller — runs the project firmware
  • Soldering kit + basic tools — one-time buy, serves every future build

Partner

Reach your Pi from anywhere — Remote desktop to the machine running this build — no port forwarding, works right from the browser.Try Getscreen.me
1

COMPAREE VERDICT

This is a classic control systems demo: a ball rolls on a plate, a camera tracks it, and two servos tilt the plate to keep it balanced or make it follow patterns. It is mesmerising to watch and genuinely useful if you are learning PID control or computer vision on an embedded system. The CAD and code are all there, and the electronics are standard maker fare — ESP32, a camera module, two servos, and a handful of linkages. The hard part is not the build, it is the tuning. PID constants that work for one ball and one frame rate will not work for another, and the repo does not document the process. You will spend more time tweaking gains than soldering. If you have never tuned a PID loop before, this will teach you by trial and error, but it will not be quick. The other gotcha: the camera needs a clear unobstructed view from directly above, which means your desk setup matters as much as the print quality. If you want to understand closed-loop control and are comfortable iterating on parameters until it works, this is one of the best ways to learn. If you want a plug-and-play demo, you will be frustrated.

NOT IN THE REPO

  • —STL files for the platform frame and camera mount are in the repo.
  • —Arduino code is provided for the PID control loop and servo coordination.
  • —Bill of materials lists servos, camera module, ESP32, and mechanical components.
  • —No assembly guide or tuning documentation — the README is a parts list and a circuit diagram.
  • —Licence is MIT, commercial use permitted.
  • —The PID constants are hard-coded with no explanation of how to tune them for your build.

Can I build this?

PrintPlatform frame, servo mounts, camera arm — around 200g of filament, no supports needed for most parts.
BuyESP32, OV7670 or similar camera module, 2× MG996R servos, ball bearings for linkages, ping-pong ball or similar lightweight ball.
ToolsSoldering iron, small screwdrivers, multimeter for checking servo power draw, computer with Arduino IDE and USB cable.
SkillsIntermediate electronics and basic 3D printing. You need to be comfortable flashing firmware, wiring servos, and iterating on PID constants until the system stabilises.
TimeA weekend to assemble and wire, then another few evenings to tune the control loop and get smooth motion.
Cost$$ — servos and the camera module dominate, total around £40–60 depending on where you source parts.
SafetyServos draw several amps under load — use a dedicated power supply, not USB. No other hazards beyond ordinary electronics care.

Build at your own risk. Projects involve tools, electronics and sometimes mains voltage — follow the creator’s safety notes.

A desktop 3D printer that prints in full colorPartner · Kickstarter
A desktop 3D printer that prints in full color

HeyGears G1: 10M+ colors and transparent parts in one print, plus UV printing on flat objects. Figures, parts and labels — no painting.

See how it prints

Gallery

upload://cmrvtahlf0gihri1z9d7yaun7/upload-e42eacef.jpg

Start here

Navigation into the creator’s own docs — we don’t rewrite the guide, we route you to the source.

  1. 1.Print the frame and mounts(STLs are ready to print, no supports needed for most parts.)
  2. 2.Order the electronics (README lists exact servo model and camera module — match them to avoid re-tuning.)
  3. 3.Wire the servos and camera to the ESP32 (Diagram is clear but minimal — double-check servo power supply is adequate.)
  4. 4.Flash the Arduino code(Default PID constants are in the code — you will tune them later.)

KNOWN ISSUES

  • The camera module matters. An OV7670 from one supplier may have different frame rates or lens distortion than another — and the PID loop is sensitive to both. Buy from a known source or budget time to recalibrate.
  • PID tuning is not documented. The constants in the code worked for the original builder's setup, but your ball weight, servo response time, and frame rate will differ. Expect to spend several hours adjusting Kp, Ki, and Kd until it stabilises.
  • Servo power supply must be separate from the ESP32. USB cannot supply enough current — the servos will stutter or reset the board. Use a bench supply or a dedicated 5V adapter rated for at least 3A.
  • The camera mount must be rigid. Any flex in the arm will add latency and make the control loop oscillate. Print it in thick walls or add a support strut if your filament is flexible.
  • Ball choice affects behaviour. A ping-pong ball is light and fast, a steel bearing is heavy and slow. The demo uses a ping-pong ball, and the PID constants assume that mass and drag.
  • No assembly guide exists. The README assumes you can infer the mechanical linkage from the CAD and the circuit from the diagram. If you have never built a servo-driven mechanism, you will reverse-engineer it from the photos.

Can I use different servos?

You can, but the PID loop is tuned for the speed and torque of MG996R servos. Faster or slower servos will require re-tuning all three constants, and weaker servos may not have enough torque to tilt the platform smoothly under load.

What is the frame rate of the camera?

The OV7670 module runs at around 30fps in the default configuration. The control loop updates every frame, so latency is around 33ms. A faster camera would improve response but require code changes.

How do I tune the PID constants?

Start with Kp only, increase it until the ball oscillates, then back off 30%. Add Ki to eliminate steady-state error, then add Kd to damp overshoot. The repo does not document this — it is standard PID tuning, but you will learn it by doing.

Can it follow patterns or just balance?

The firmware includes setpoint tracking, so you can command it to trace circles, figure-eights, or any path. The demo video shows circle-following. The setpoint is hard-coded — there is no joystick or GUI.

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Discussion1

FROM THE COMPAREE TEAM

The whole trick is tuning the PID loop until it stops oscillating — and the repo does not document the process. How long did yours take to stabilise?

CompareeTEAM1mo agoedited

Practical notes from our verification: the repository includes all the STLs, firmware, and a wiring diagram, but there is no step-by-step assembly guide or PID tuning documentation. The demonstration footage is hypnotic, but every builder will spend more time adjusting control constants than printing parts. The camera module and servo choice matter — mismatches in frame rate or torque will require complete re-tuning. This is one of the best open projects for learning closed-loop control, but it assumes you are comfortable iterating on parameters without a manual.

aaedmusa

A control systems project built to demonstrate PID tuning and real-time computer vision on an embedded platform. The builder shared the full design in 2023 and it remains one of the clearest examples of a ball-balancing system for makers.

GitHub

Star the project on GitHub

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